1. Field of the Invention
The invention relates generally to the field of imaging a target and more particularly to the field of imaging the contents of a moving target.
2. Description of the Related Art
In this time of increased security concerns, authorities are continually looking for ways to improve national security through imaging technology. Additionally, law enforcement continues to battle drug, stolen goods and people trafficking both at the borders and within the borders of the United States through nonintrusive x-ray and gamma-ray imaging. There is a balance that must be struck between the desire to check the contents of vehicles for illegal and/or potentially hazardous materials and the desire to protect the drivers of the vehicles and to minimize the impact of the investigation on the flow of commerce.
Currently available vehicle and cargo imaging systems, particularly those directed towards the imaging of moving targets, i.e., trucks, etc., utilize stop-and-go procedures that require manual control of the scan process. For example, current systems require the driver of the moving target to (1) stop the vehicle in a scanning zone, (2) certain systems require the driver to exit the vehicle and go a safe distance from the scanning zone to avoid potential exposure to the imaging radiation and, (3) certain systems require the driver, or some third party, to manually initiate the scanning of the vehicle. Further, many of the systems that are currently available for such imaging, utilize a high power x-ray source for the imaging radiation.
By way of specific example, a particular known vehicle and cargo imaging system and process is described as follows. The driver approaches the first of 3 traffic signals. The first signal “enter” is green when there is no vehicle sensed between opposing source and detector towers defining the scan area, and red when there is a vehicle in the scan area. When the “enter” signal turns green the driver approaches a driver arm and the second traffic signal, which is red at this point. The “enter” of the first traffic signal also turns red, prohibiting any other vehicles from entering the scan area. Sensors detect the presence of the vehicle and a flashing yellow light on the driver arm engages. This prompts the driver to press the driver pushbutton located on a panel outside of the vehicle before the driver arm. This pushbutton sends a signal to an operator console notifying the operator that the driver is ready for his vehicle to be scanned. The operator presses the blinking “scan” button on the operator console and the shutters to the scanning source are opened. At this time, the second “scan” traffic light turns green and the driver proceeds through the scan area. As the vehicle exits the scan area, sensors detect the lack of a vehicle and automatically close the shutters to the scanning source. At this point, the first “enter” traffic signal turns green for another vehicle to proceed to the driver arm. Lastly, the “Exit” button on the operator panel lights up and the operator can depress the button to change the third traffic signal from red to green, thus allowing the vehicle to completely exit the area. This whole process takes approximately 20 seconds for a nominal scan.